Introduction: Recording from the human brain offers unique functional insight and the potential to advance therapeutic modalities. However, the practical yield from these methods remains low because our technology is limited, and faster and denser recording techniques are needed to better understand and modulate the brain.
Methods: A novel high-density intraoperative electrode was developed through collaboration between materials science, electrical engineering, and neuroscience. The electrode contacts are made using Poly(3,4-ethylenenedioxythiophene) (PEDOT), a material with a much higher permeability to charge ions than traditional metal electrodes. The contacts are connected to custom preamplifier and amplifier circuits engineered for intraoperative use. The electrode base is made from parylene, a thin, flexible layer that conforms to the gyri and sulci of the brain. The prototype electrode used 6 large recording contacts (1mm diameter) for reference, and had 56 smaller contacts (40 µm diameter). The system is capable of recording from 256 channels at 20kHz, although only 62 electrodes were used in initial testing.
Results: The first intraoperative recordings using the PEDOT electrodes were performed during a left-sided lobectomy for mesial temporal epilepsy. Recordings were performed from the posteriolateral temporal lobe in proximity to Wernicke's area. While awake, the patient listened to auditory cues and performed lexical decision tasks. During these tasks, the electrode captured high frequency neural activity, and clear differences in activity could be observed between resting state, patient task, and anesthesia.
Conclusions: We demonstrate intraoperative application of a high spatial- and temporal- resolution electrode. Although the electrode is currently being tested in conjunction with basic science research, the ease of use and quality of recordings suggests practical application in the clinical setting. Direct collaboration across fields has allowed for a rapid sequence from design to prototype, and continues to yield exciting new directions in electrode configuration and design.
Patient Care: Development of higher density, higher resolution electrodes suitable for intraoperative use will improve resolution and precision of ablative techniques and resection. These electrodes also have high potential for long-term recordings, such as with brain-machine interfaces, seizure detection, or closed loop stimulation.
Learning Objectives: - Development of a novel recording electrode using parylene C as substrate and PEDOT as electrode contact.
- Initial test and application of the new electrode format intraoperatively shows modulation of neuronal activity during a task